This paper examines the impact of the network modification produced by the replacement of an existing conventional generator with a high voltage directly connected generator on the adequacy of existing circuit breakers distributed throughout a high voltage transmission network. The significance of generator design changes is assessed by comparing the critical fault types producing maximal circuit breaker current through each breaker in the original and modified networks. In the majority of cases the impact of even significant generator design changes on the nature of these "critical fault types" is restricted mainly to breakers in the immediate vicinity of the generator of interest. Finally, analytical expressions quantifying the influence of generator design on the current flows produced by faults through circuit breakers distributed network-wide are developed to clarify the results obtained from simulation.